Question: What is the greatest common factor of $40$ and $5$ ? Another way to say this is: $\operatorname{gcf}(40, 5) = {?}$
Solution: The greatest common factor is the largest number that is a factor of both $40$ and $5$ The factors of $40$ are $1$ $2$ $4$ $5$ $8$ $10$ $20$ , and $40$ The factors of $5$ are $1$ and $5$ Thus, the greatest common factor of $40$ and $5$ is $5$. $\operatorname{gcf}(40, 5) = 5$